chore(main): release 2.0.4

[release-please[bot]]

:robot: I have created a release beep boop

2.0.4 (2023-04-28)

Bug Fixes

• deps: Update dependency mkdirp to v3 (#500) (fa5ccbe)
• Fix Ruby and PHP namespaces (#499) (5c65bb4)

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[release-please[bot]]

:robot: Release is at https://github.com/googleapis/google-cloudevents/releases/tag/v2.0.4 :sunflower: